Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$162.39	10.325%	$179.1568	$179.16	$179.15	$179.20
Purchase #2	$136.30	6.387%	$145.0055	$145.01	$145.00	$145.00
Purchase #3	$89.82	8.670%	$97.6074	$97.61	$97.60	$97.60
Purchase #4	$17.31	5.595%	$18.2785	$18.28	$18.30	$18.30
Purchase #5	$175.56	12.108%	$196.8168	$196.82	$196.80	$196.80
Purchase #6	$112.40	5.830%	$118.9529	$118.95	$118.95	$119.00
Purchase #7	$112.30	13.699%	$127.684	$127.68	$127.70	$127.70
7 purchase totals =	$806.08		$883.5019	$883.51	$883.50	$883.60